1. Technical Field
The present disclosure relates to a wide band antenna and, particularly, to a wide band antenna for mobile communication.
2. Description of Related Art
Referring to FIG. 1, an antenna 1 of related art for mobile communication is shown. The antenna 1 is used for receiving radio frequency (RF) signals and radiating corresponding radio waves. The antenna 1 includes a radiation element 11, a dielectric element 12, a ground surface 13, a microstrip feeder 14, and a connector 15. The radiation element 11, the ground surface 13, and the microstrip feeder 14 are all conductive. The dielectric element 12 is positioned between the radiation element 11 and the ground surface 13. The radiation element 11, the dielectric element 12, and the microstrip feeder 14 are supported by the ground surface 13. The radiation element 11 is a rectangle shaped including a first side 16 and a second side 17. The first side 16 is adjacent to the second side 17. The microstrip feeder 14 is connected to the midpoint of the first side 16 and perpendicular to the first side 16. If a length of the second side 17 of the radiation element 11 is L1, a frequency of the antenna 1 can be computed by the following formula:
  f  =      0.49    ⁢          V              L        ⁢                              ɛ            r                              where, ∈r represents a dielectric coefficient of the dielectric element 12. V represents a velocity of electromagnetic wave. Because ∈r and V are both constant, the frequency f of the antenna 1 is determined by the length of the adjacent side of the first side 16 to which the microstrip feeder 14 is connected. Due to the two adjacent sides of the first side 16 both are L1, only one frequency is generated by the antenna 1.